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MayaMan Scanline Options

This dialog contains options that are specific to renderers that support scanline rendering. These options apply to PRMan, and may or may not apply to other particular scanline renderers.

General

Compress RIB Files

When this option is on, the RIB files output by MayaMan will be compressed using the gzip algorithm. This results in much smaller files, but may result in slower RIB creation and RIB reading times.

Clamp to Alpha

When this option is on, all color values being output will be clamped to their alpha values. Shaders outputting color values greater than one can sometimes result in a color greater than the alpha, which can lead to compositing problems.

Binary Dicing

When this option is on, the renderer will only dice patches into grids of micropolygons of a size that is a power of two. This can be used to prevent cracking on patches with high curvature.

Bucket Size

The renderer renders images with a tiling algorithm, resulting in much lower memory usage. It may be advantageous to increase the size of these buckets to make very simple scenes render quicker, or to reduce the bucket size for memory intensive scenes.

Eye Splits

The renderer cannot tolerate primitives spanning the camera eye plane, and so they split such primitives down to smaller pieces in an attempt to get around this problem. They will attempt to split such primitives 10 times before discarding the remaining spanning pieces. This recursive splitting can be time and memory intensive, so you may want to reduce the number of recursions with this parameter.

Extreme Displacement

Shaders that displace their surface a large amount can end up using a lot of memory. Because of this, if the renderer sees an 'extreme' displacement, it will use a different algorithm which uses less memory. What it deems to be extreme is 32 scanlines by default, but this can be changed with this parameter.

Grid Size

Determines the maximum number of micropolygons to be shaded at one time. Shading large grids can be faster, but increases the memory usage of the renderer.

Backface Tolerance

The renderer will cull any single sided primitives that are facing away from the viewpoint. Usually this means their angle to the viewer is greater than 90 degrees. However, this can sometimes lead to artifacts, for example if displacement results in part of a surface curling back around to face the viewpoint. Using this backface tolerance option, yuo can increase the angle at which the renderer will cull primitives. A value of 20 here will mean any objects facing greater than 110 degrees away from the viewer will be culled.

Shadow Bias

The bias value when generating shadow maps can be set here. This is not normally needed when using midpoint shadow maps, but can be necessary with other shadow map sampling types. Increase this parameter to reduce objects that appear to be self-shadowing.

Z-Threshold

The renderer will only render objects into shadow maps that are completely opaque by default. Using this option you can set an opacity color, and any objects whose opacity is at least that color will be rendered into the shadow maps.

O-Threshold

If you have a large amount of semi-transparent objects overlapping each other, the renderer may end up spending a lot of time rendering objects when the pixel is already effectively opaque. By setting the 'othreshold' value, you can tell the renderer to assume that a pixel is completely opaque once it has reached a certain threshold, which you can specify with this option.

Flatness

This parameter controls how far from the true geometric surface is tolerable. The value is expressed in pixels.

Motion Factor

If you have objects that are motion blurred over a large distance in screen space, the renderer may be wasting a lot of time by finely shading the object. Turning this option on will cause the renderer to greatly increase the shading rate of objects that are highly motion blurred. A value of zero will turn this off, a value of 1.0 is good for most cases, and larger values for extreme motion blur.

Shell Output

Display Progress

When this option is on, the renderer will output a percentage value for how far it is through the render computation. This is output to the shell that the renderer is running in.

Some renderers use a -silent flag to turn off progress while others use -progress to turn it on, either way this switch is controls it.

Display Debug Info

This causes the renderer to output debugging information. This can result in a lot of output, but can be useful in determining what is happening when the image output contains artifacts.

Output Info

Controls how much informational data is output by the renderer. You can get various levels of rendering statistics.

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